Chronic toxicity of diclofenac, carbamazepine and their mixture to Daphnia magna: a comparative two-generational study

The chronic toxicity of diclofenac (DCF) and carbamazepine (CBZ) as separate substances and in conjunction with their mixture on Daphnia magna was assessed in the parental (F0) and first filial (F1) generations. The second (F1-B2) and fifth (F1-B5) broods of F1 offspring were investigated and compared. Both drugs and their mixture were exposed to each generation of Daphnia magna for 21 days with life history, behavioural and gene expressions as measured endpoints. After the parental exposure, offspring from these two broods were transferred to a clean medium for a 21-day recovery. Exposure to diclofenac, carbamazepine and their mixture significantly inhibited growth, reproduction, swimming activities, heart rate, thoracic limb activities, reproductive and antioxidant-related genes in the parental as well as the first filial generations. These effects were relatively greater in the F1 generation. This indicates that Daphnia magna's sensitivity improved while its fitness declined over the two generations, which is an indicator of greater energy requirements for maintenance. Besides, the significant inhibition in the antioxidant-related genes implies that oxidative stress occurred in Daphnia magna under the exposure to these drugs. The significant reduction in the reproductive output, moulting frequency and cyp314 gene expression as a result of exposure to CBZ simultaneously obtained herein may indicate that this drug could act as an endocrine disruptor. Most of these significant effects were not recoverable after the 21-day recovery period. The findings reported herein highlight the necessity to include maternal effects in environmental risk assessment processes, considering that pollutant effects are underestimated during single-generational exposure.

Biological uptake, depuration and biochemical effects of diclofenac and carbamazepine in Carassius carassius

The uptake and depuration kinetics of diclofenac and carbamazepine alone at an environmentally relevant nominal concentration of 2 μg/L and in combination at a concentration ratio of 1:1 with total concentration of 4 μg/L were evaluated in Carassius carassius after 7 d uptake and depuration. Also, the biochemical effects of both drugs alone at nominal concentrations of 2 and 10 μg/L as well as in combination with total concentrations of 4 and 20 μg/L were investigated in Carassius carassius after 7 d exposure followed by 10 d recovery. In the single treatments, steady-state BCFs measured after the 7 d exposure were 73.05, 49.71, 38.01 and 24.93 L/kg for diclofenac and 9.25, 8.99, 5.29 and 4.11 L/kg for carbamazepine in the liver, brain, gill and muscle of Carassius carassius, respectively. Comparatively lower BCFs were measured in the tissues of Carassius carassius for both drugs in the combined treatments. Acetylcholinesterase activity in the brain was significantly induced by diclofenac while carbamazepine and the mixtures significantly inhibited it during all the exposure days as well as after the 10 d recovery in all treatments. This indicates that Carassius carassius could not recover from the neurotoxic effects caused by carbamazepine unlike the inductive effect caused by diclofenac which was recoverable after 10 days. A significant increase in the activities of 7-ethoxyresorufin O-deethylase and glutathione s-transferase for individual and mixed pharmaceuticals suggest that metabolism and detoxification of both drugs took place in the liver of Carassius carassius. Also, a significant increase in the activities of superoxide dismutase, catalase, glutathione reductase and malondialdehyde contents in the individual and mixture treatments mean that the antioxidant defence system of Carassius carassius was triggered to fight against oxidative stress but lipid peroxidation still occurred. However, Carassius carassius recovered from all these increases (superoxide dismutase, catalase, glutathione reductase and malondialdehyde) after the 10 d recovery, suggesting that oxidative damage is reversible. Our results indicate that both drugs at environmentally relevant concentrations might cause adverse effects in Carassius carassius and other fish species.

Distribution, sources and human risk of perfluoroalkyl acids (PFAAs) in a receiving riverine environment of the Nanjing urban area, East China

In recent years, perfluoroalkyl acids (PFAAs) have become ubiquitously distributed in water environments, especially in riverine waters receiving effluents from wastewater treatment plants (WWTPs) in urban areas. With rapid economic development, China has become the main market of manufacturing and consuming fluorinated products. While studies concerning PFAAs on dimension of urban water system are scarce. To elucidate the distribution patterns of PFAAs using multi-matrices, the effects of spatial-temporal factors on the partition behaviors of PFAAs were investigated in different riverine environments in the downtown area of Nanjing, East China. Predominated by perfluorooctanoic acid (PFOA), sum PFAAs (∑PFAAs) in the water phase were with concentrations of 0.8˜274.6 ng/L, characteristically higher in the dry season and lower in the wet season. The composition profiles in sediments (∑PFAAs 0.8˜11.4 ng/g dry weight) differed from that in water, being with a larger proportion of longer-chain PFAAs. The main sources of PFAAs in water were identified as industrial discharge, uncontrolled sewage discharge or WWTP effluents, surface runoff and nonpoint sources. The discharge fluxes of ∑PFAAs from Nanjing City can reach at 916.5 g/d for the Qinhuai River and 134.1 g/d for WWTPs along the Yangtze River. Fish have been shown to accumulate PFAAs in various tissues, with bioaccumulation positively correlated with perfluoroalkyl chain length. The hazard indexes associated with consumption of river fish were estimated low for Nanjing local population.

Occurrence, spatial-temporal distribution and ecological risks of pharmaceuticals and personal care products response to water diversion across the rivers in Nanjing, China

Water diversion projects have been continuously used to alleviate water quality issues that arise during urbanization. However, studies about whether it has possible effects on the status of pharmaceutical and personal care products (PPCPs) are limited. In this study, the occurrence trends and spatial-temporal distribution characteristics of 50 PPCPs were investigated in surface water, suspended particulate matter (SPM) and sediments in Nanjing urban rivers under the background of the water diversion project from the Yangtze River to the Qinhuai River. In the four field campaigns that were embarked on April to July 2018, a total of 40, 38 and 24 PPCPs were detected in surface water, SPM and sediments, respectively, with overall concentrations of 138-1990 ng/L, 3214-33,701 ng/g and 12.1-109 ng/g dry weight (dw) among nine sampling sites. The excessive concentration of caffeine (20.6-905 ng/L) may be evidence of the direct discharge of untreated sewage and an obvious indicator of the overall concentrations of PPCPs. The PPCPs contamination levels in surface water were increased along with the direction of the water diversion in urban runoff, and decreased by 8-31% due to the increase in volume attributable to the water diversion. The distribution coefficients (K_d) of pollutants in the SPM-water phases (3.0-5.6 L/kg) were two orders of magnitude higher than those in the sediment-water phases (0.3-3.3 L/kg). And the positive correlations between their log K_ow and SPM-water log K_d values indicated SPM was the important carrier determining the fate of organic UV filters. Furthermore, the results of ecological risk assessment demonstrated that although the increase in the volume of water caused by the water diversion reduced the overall ecological risks of PPCPs in urban rivers, the current contamination level still represents high risks to algae and fish.

Bioconcentration of the antiepileptic drug carbamazepine and its physiological and biochemical effects on Daphnia magna

Owing to its persistence, carbamazepine an antiepileptic drug is regularly detected in the aquatic environment. The motive for our research was to assess the bioconcentration, physiological and biochemical effects of carbamazepine in Daphnia magna. A 48 h aqueous exposure of carbamazepine yielded bioconcentration factors of 202.56 and 19.95 in Daphnia magna for the respective nominal treatments of 5 and 100 µg/L. Apparently, the inhibition of the capability of Daphnia magna to obtain food attributable to carbamazepine exposure will reduce their fitness to reproduce as well as to grow. Also, a significant alteration in the phototactic behaviour of Daphnia magna exposed to carbamazepine is maladaptive since it will increase their chance of being preyed upon in the surface water during daylight. Again, a significant decline in the acetylcholinesterase activity observed herein brings to light the neurotoxicity of carbamazepine to Daphnia magna. Moreover, significant inhibition of the superoxide dismutase, catalase and glutathione reductase activities coupled with the simultaneous induction of the malondialdehyde content imply that carbamazepine evoked a life-threatening oxidative stress that overpowered the antioxidant defence system of Daphnia magna. These observations confirm that carbamazepine can accumulate and consequently cause negative physiological and biochemical changes to wild Daphnia magna populations.

Bioconcentration, behavioral, and biochemical effects of the non-steroidal anti-inflammatory drug diclofenac in Daphnia magna

The non-steroidal anti-inflammatory drug (NSAID) diclofenac is one of the most frequently studied as well as controversially discussed pharmaceutically active drug on the subject of its relevance to the environment. This study was conducted to assess the bioconcentration potential of diclofenac and its behavioral and biochemical effects in Daphnia magna. The bioconcentration factors of diclofenac determined after 48 h of aqueous exposure in Daphnia magna were 70.94 and 8.02 for the nominal exposure concentrations of 5 and 100 μg/L, respectively. Diclofenac exposure obviously decreased the filtration and ingestion rates of the daphnids. A significant increase of the acetylcholinesterase activity that was observed in this study indicates that diclofenac might not have neurobehavioral toxicity in Daphnia magna. Significant induction of malondialdehyde content is an indication of overproduction of reactive oxygen species leading to oxidative damage in daphnids after diclofenac exposure. Moreover, significant inhibition of the superoxide dismutase, catalase, and glutathione reductase activities implies that the antioxidant defense system of Daphnia magna was overwhelmed. Also, significant inhibition of glutathione s-transferase activity might point to the fact that the enzyme was not capable to detoxify diclofenac in Daphnia magna. These findings indicate that diclofenac can accumulate and consequently stimulate behavioral and biochemical disturbances in Daphnia magna.

Occurrence and ecological risk assessment of pharmaceuticals and personal care products in Taihu Lake, China: a review

The rationale behind this paper was to review the available data regarding the current knowledge on the levels and trends of pharmaceuticals and personal care products (PPCPs) in Taihu Lake. The ecological risk associated with some of the PPCPs was also assessed. 36 PPCPs have been detected in the water, sediment and biota of Taihu Lake. These contaminants primarily emanate from anthropogenic activities in and around the lake. The northern part of the lake is highly polluted as compared to other parts because it receives most effluents from wastewater treatment plants (WWTPs), and domestic and industrial waste discharge from developed cities nearby. Based on the risk quotient (RQ) values, ciprofloxacin, ofloxacin, 17β-estradiol, roxithromycin and tetracycline may present a high ecological risk to organisms living in Taihu Lake. Regular monitoring is required to check the levels of PPCPs as they are regularly released into the lake. Investigations into the joint toxicities of PPCPs to aquatic organisms and the spread of antibiotic-resistant bacteria and genes in Taihu Lake are highly recommended. Special attention in terms of policy and research should be given to the northern part of the lake.

Responses of antioxidant and biotransformation enzymes in Carassius carassius exposed to hexabromocyclododecane

The ubiquitous existence of hexabromocyclododecane (HBCD) in environmental matrices has made it attractive to both field investigators as well as laboratory researchers. However, literature on the biological effects caused by HBCD on aquatic vertebrates seldom exist. This has inevitably increased the difficulty of toxicological assessment in the aquatic environment. Juvenile crucian carp (Carassius carassius) were exposed (flow-through) to different concentrations of technical HBCD (nominal 2, 20, 200 μg L^-1) for 7 days to determine the responses of antioxidant and biotransformation enzymes. HBCD was found to be increasingly bioconcentrated in the fish livers as time proceeds. Also, the contribution of α-HBCD exhibited an enhancement from 13% in the exposure solutions to 24% in crucian carp, still much lower than in wild fishes (ca. 80%). HBCD induced activities of antioxidant enzymes in most cases, as well as increased level of lipid peroxidation. In contrast to the weak response of 7-ethoxyresorufin-O-deethylase (EROD), 7-pentoxyresorufin-O-depentylase (PROD) activity was generally induced in a time-dependent manner with peaks at day 2. Phase II enzyme Glutathione-S-transferase (GST) showed a dose-dependent induction with maximums in the 20 μg L^-1 treatment at all the four timepoints of 1, 2, 4 and 7 days. Some enzymatic responses showed good associations, indicating coordinated functions. To sum up, tHBCD exposure in the present circumstance had produced an ecological stress to crucian carp. The low levels of biotransformation and slow rates of bioisomerization suggest a possible long-term toxic effect, especially around HBCD point sources.

Bioconcentration and effects of hexabromocyclododecane exposure in crucian carp (Carassius auratus)

As a cycloaliphatic brominated flame retardant, hexabromocyclododecane (HBCD) has been widely used in building thermal insulation and fireproof materials. However, there is little information on the bioconcentration as well as effects with respect to HBCD exposure in the aquatic environment. To investigate the bioconcentration of HBCD in tissues (muscle and liver) and its biochemical and behavioural effects, juvenile crucian carp (Carassius auratus) were exposed to different concentrations of technical HBCD (nominal concentrations, 2, 20, 200 μg/L) for 7 days, using a flow-through exposure system. HBCD was found to concentrate in the liver and muscle with a terminal concentration of 0.60 ± 0.22 μg/g lw (lipid weight) and 0.18 ± 0.02 μg/g lw, respectively, at an environmentally-relevant concentration (2 μg/L). The total thyroxine and total triiodothyronine in the fish plasma were lowered as a result of exposure to the HBCD. Acetylcholinesterase activity in the brain was increased, while swimming activity was inhibited and shoaling inclination was enhanced after exposure to 200 μg/L HBCD. Feeding rate was suppressed in the 20 and 200 μg/L treatment groups. In summary, HBCD concentrations 10-100× higher than the current environmentally-relevant exposures induced adverse effects in the fish species tested in this study. These results suggest that increasing environmental concentrations and/or species with higher sensitivity than carp might be adversely affected by HBCD.

The effects of dissolved organic matter and feeding on bioconcentration and oxidative stress of ethylhexyl dimethyl p-aminobenzoate (OD-PABA) to crucian carp (Carassius auratus)

Bioconcentration of UV filters in organisms is an important indicator for the assessment of environmental hazards. However, bioconcentration testing rarely accounts for the influence of natural aquatic environmental factors. In order to better assess the ecological risk of organic UV filters (OUV-Fs) in an actual water environment, this study determined the influences of dissolved organic matter (DOM) (0, 1, 10, and 20 mg/L) and feeding (0, 0.5, 1, and 2% body weight/d) on bioconcentration of ethylhexyl dimethyl p-aminobenzoate (OD-PABA) in various tissues of crucian carp (Carassius auratus). Moreover, oxidative stress in the fish liver caused by the OD-PABA was also investigated by measuring activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), and levels of glutathione (GSH) and malondialdehyde (MDA). The bioconcentration of OD-PABA in the fish tissues was significantly decreased with the presence of DOM indicating a reduction of OD-PABA bioavailability caused by DOM. The bioconcentration factors (BCFs) decreased by 28.00~50.93% in the muscle, 72.67~96.74% in the gill, 37.84~87.72% in the liver, and 10.32~79.38% in the kidney at different DOM concentrations compared to those of the non-DOM treatments. Significant changes in SOD, CAT, GST, GSH, and MDA levels were found in the DOM- and OD-PABA-alone treatments. However, there were no significant differences in the SOD, CAT, GST, and MDA levels found when co-exposure to OD-PABA and DOM. Feeding led to lower OD-PABA concentrations in the fish tissues, and the concentrations were decreased with increasing feeding ratios. BCFs in various tissues reduced by 39.75~72.52% in the muscle, 56.86~79.73% in the gill, 66.41~87.50% in the liver, and 75.88~89.10% in the kidney, respectively. In the unfed treatments, the levels of SOD and MDA were significantly higher than those of the fed ones while GST and GSH levels were remarkably inhibited indicating the enhanced effect of starvation to oxidative stress. There was no markedly alternation of the biomarker levels observed between different fed treatments. In conclusion, our study indicated that both DOM and feeding reduced bioconcentration of OD-PABA and alleviated oxidative stress to some extent in the crucian carp.

Adsorptive removal of aqueous bezafibrate by magnetic ferrite modified carbon nanotubes

MFe₂O₄/CNTs were synthesized and successfully applied for the removal of aqueous bezafibrate. The adsorption behavior and mechanism were elucidated in detail.